Turbodrill tachometer



Nov. 1, 1960 D. L. WEBB 2,958,821

TURBODRILL TACHOMETER Filed April 1,1957 2 Sheets-Sheet 1 DAV] D l...WEBE5 INVENTOR.

FIG. 1. BYW%/ A TTORNEY Nov. 1, 1960 D. L. WEBB TURBQDRILL TACHOMETERFiled April 1, 195'? 2 Sheets-Sheet 2 INVEVTOR.

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United States Patent TURBODRILL TACHOMETER David L. Webb, Dallas, Tex.,assignor to Dresser Operations, Inc., Dallas, Tex, a corporation ofCalifornia Filed Apr. 1, 1957, Ser. No. 649,781

3 Claims. (Cl. 324-70) This invention relates to improvements in themethod and apparatus for determining the rotary speed of a mud driventurbine which is in operation at the bottom of a well, more particularlyof the type of deep oil or' water wells.

It has been found, in the drilling of deep wells with the so called mudturbine as a source of rotational energy for the bit that it isessential for economical operation to know rather precisely therevolutions per minute of the rotor which is directly proportional tothe revolutions per minute of the bit. It will be apparent that the rateof penetration of the drill which is actually the measure ofeffectiveness of the drilling operation, is a function of the load onthe drill and its rotary speed.

When it is appreciated that the operator of the drill rig is operatingthe bit which may be several thousand feet to several miles deep in acomparatively small well, it will be realized that his only controls aremud pressure and rate of flow and the actual load on the bit. It isessential, therefore, that he be constantly advised as to the rotaryspeed of the bit.

While the need of such information has been recognized and someinventors have suggested solutions as for example requiring the use ofelectrical cables, it is quite apparent that these solutions are notfeasible, either because of excessive cost, technical complications, ormere incomplete or inaccurate reporting.

More recently a well logging system has been disclosed in which signalsat the bottom of the well could be encoded through actuating means and,using the drilling fluid as the transmission medium, could be decoded atthe top of the well. Thus not only are the results constantly availableto the drilling operator but there isno need for auxiliary conductors,cables or the like.

An adaptation and improvement on this invention is shown in the Otis eta1. Patent 2,700,131 in which the signals impressed on the drillingfluid are at spaced intervals of such a type that the interval isintegrated to show a characteristic related to the original signal.While such a system is effective for the intermittent reporting ofvarious electrical conditions, it is considered too elaborate forroutine reporting of the variable rotary speed of a device such as a mudturbine and its bit. It would be too slow for normal operatingconditions as a drilling operator might lose his bit due to changes ofspeed between reporting intervals.

My invention, while specifically concerned with the continuous andhighly accurate measure of the revolutions per minute of a bit (orturbine rotor) at the bottom of a hole which is rapidly deepening, isnecessarily rugged, simple and of low cost. It is primarily intended forthe single purpose and embodies only those elements which make anaccurate and direct reading possible. It is to be noted however thatrecognition must be made of the environment of the drill and therecording device and the presence of surface interferences such as themud The following description taken in connection with the attacheddrawings is a disclosure of a preferred form of embodiment of myinvention.

In the drawings:

Figure 1 is an elevational view, partly schematic and partly inlongitudinal section illustrating the general arrangement of theapparatus as employed in connection with a typical drilling well.

Figure 2 is a central, vertical, partial cross-sectional view of theupper part of a mud driven turbine.

Figure 3 is a transverse cross-section through Figure 2 substantially onthe line 3-3 thereof.

Figure 4 is a central, vertical, partial cross-sectional view of theupper part of a modified type of mud driven turbine.

Figure 5 is a transverse cross-section taken substantially on the line55 of Figure 4.

Figure 6 is a transverse cross-section substantially on the line 6--6 ofFigure 4.

Referring to Figure 1 in which the general disposition of the apparatusof the invention is shown in relation to a conventional drilling rig anddrilling well, 10 is the lower uncased portion of the bore hole and 11the upper portion of the bore hole in which the usual surface string orconductor string of casing 12 has been set. Within the bore hole and atthe surface above the bore hole is shown a conventional drilling rigcomprising a drill bit 13, a turbodrill 14 and a drill stern composed ofdrill pipe 15 connected at its upper end to a swivel 17 which in turn issuspended from a traveling block hook 18, traveling block 19, drillingline 20 and crown block located in the top of the derrick 22.

The mud circulation passage extending through the drill bit 13,turbodrill 14 and drill stem 15 extends through the swivel 17 and isconnected through suitable flexible connections or hose 31 to thedischarge connection 35 of a drilling fluid circulating pump 36. Thedrilling fluid circulating pump 36 takes suction through pipe 38 from abody of drilling fluid contained in a mud reservoir or sump 40. Theupper end of the surface casing 12 which provides a return path forcirculating drilling fluid there below is provided with a lateral outletpipe 42 which extends to and discharges into the fluid reservoir 40. Asurge chamber 45 is preferably connected to the discharge 35 of thedrilling fluid circulating pump 36 for the purpose of smoothing out orreducing the pump discharge pressure fluctuations.

In normal operations with the turbodrill, the drilling mud is pumpedfrom pump 36 through the drill pipe 15 and the turbodrill 14 in such amanner as to rotate the bit 13. The discharge from the Well bore asbefore mentioned not only carries the cuttings out of the hole but tendsto plaster up the wall in the usual manner.

In accordance with present practice, the turbodrill operates in such amanner as to rotate the bit at approximately 450 to 800 revolutions perminute under optimum conditions. The pump 36 which is a high pressure,low speed pump usually of the triplex type normally operates atapproximately 60 to 70 revolutions per minute.

In accordance with my invention, the rotational speed of the turbine maybe continuously reported at the drill rig by the following means.

Within the turbodrill casing 14 is normally mounted a rotor membergenerally designated at 50 in Figure 2. This is diagrammatically shownand is a part which can be attached directly to the rotor shaft or maybe a part of the rotor itself. The rotor member 50 has a cap 51 and isprovided with one or more openings 52 as shown in Figure 3 through whichthe mud flows from the drill pipe 15 through the turbodn'll casing 14into the turbine mounted below.

Adjacent the mud opening 52 I provide one or more flow interrupter orrestrictor elements generally indicated at 54 in such a manner that asthe rotor turns there will be some obstruction to flow as the opening 52passes the interrupter head. This in turn will generate a pressure pulseon the fluid stream which is substantially instantaneous. Bearings 56tend to center the rotor member 50 in the turbodrill casing 14.

If two interrupter bodies 54 and 54A as shown in Figures 2 and 3 areused, there will normally be two pressure pulses per revolution. It willbe apparent that if there were more than two there would be anincreasing number in proportion to the revolutions per minute. If thereis only one, the pressure pulses are equal to the revolutions perminute.

The detection of these pressure pulses at the surface of the well isaccomplished by a suitable pressure pick up device 47 which may be ofany suitable type such as Consolidated Engineering Corporation pressuretransducer model No. 4-311 adapted to convert fluid pressurecommunicated to it from pipe 35 into corresponding values of electricalcurrent or potential. This transducer may be energized by a suitableelectrical current supply and when so energized is capable of producingan electrical output signal which is a direct function of theinstantaneous fluid pressure applied to it which pressure in the presentcase is that appearing in pipe 35.

The pressure pick up device 47 is, in turn, connected through insulatedconductors 48 to a suitable meter unit 56 which may be adapted toindicate the revolutions per minute of the rotor. While the details ofsuch meter unit are not considered a part of this disclosure, it isknown that it will normally include an amplifier, a band pass filter andusually a frequency meter. The amplifier and band pass filter may notalways be necessary, especially where the pulse is strong and sharp.

With a frequency of 450 to 800 revolutions (or pulses) per minute, ormultiples thereof, a General Radio Corporation direct reading frequencymeter Type 1178-A may be used. The band pass filter will be designed inthe usual manner to discriminate against frequencies outside the rangeof interest. A General Radio Corporation unit amplifier Type 1206-B maybe used. A tuned circuit may be automatically or manually adjusted tothe resonant frequency.

The matter of attenuation of the hydraulic signals must be taken intoconsideration based on the nature of the mud pump 36. It will beapparent that if a triplex pump operates at 70 revolutions per minute,it generates approximately 420 pulses per minute. This might tend tointerfere with reception of signals if the rotor of the turbine wasoperating at the low end of its scale and the single pulse only weresent out per revolution. While it is known that attenuation increasesrapidly with frequency, some rate of pulse generation in proportion toturbine (or bit) rotation is usually desirable.

There is however an alternate method of sending out pulses by which thestrongest signals are received. If, for example, the mud flowinterrupter is operated at a ratio of less than one under someconditions which will be hereinafter described, better results will beobtained. In this form of embodiment of the invention as shown in Figure4, the turbodrill body 14 is similarly adapted to receive a turbinerotor 50 having the mud openings 52 but is surmounted by a modified typeof cap 60. In this case as will be seen from the cross-sectional viewFigure 5, the shaft of the cap is eccentric and is adapted to receive aninternal gear 61 which in turn meshes with an external gear 62 suitablysecured to the wall of the turbodrill 14. The pinion gear 61 is providedwith a fluid passage generally indicated at 64. A suitable interrupter65 is mounted below the internal ring gear in such a position that itwill interrupt the flow of mud downwardly through the turbodrill body 14and into the opening 52. V

In view of the fact that the internal gear is eccentrically mounted withrespect to the turbine rotor there will be a gear reduction dependingupon such eccentricity so that the number of interruptions of flow canbe established as some fraction of the rate of rotation of the rotor.

In other words a frequency of interruption of one interruption for eachten revolutions or more or less depending upon the desired frequency andthe approximate rotational rate can be obtained. With a normalrotational speed of the turbine from 450 to 800 revolutions per minutewould be reflected by as low as 45 to interruptions or cycles perminute.

While it may not be possible to use the same electrical equipment asshown in the unit 56 for either the high frequency or the low frequencyoperations due to the electrical limitations of the equipment, it is ofcourse possible to substitute appropriately balanced circuits which willoperate in the range of less than one cycle per second to several cyclesper second as well as operating in the range ten to a hundred cycles persecond.

It is thus to be understood that I am not limited to either the directfrequency of rotation which may interfere with the frequency of pulse ofthe pump but can operate with either a fraction of such frequency or amultiple of such frequency.

As heretofore mentioned there are advantages in using multiplefrequencies because of the simplicity of the electrical equipmentwhereas there are advantages in using a fraction of the frequency notonly because of the much stronger pulse, but the sharper recognition ofthe pulse and less attenuation in the well.

While I have shown a simplified and schematic construction ofinterrupter it will be appreciated that modifications in design will bemade to fit the particular type of turbodrill construction. Theinvention is applicable to either the direct driven bit or to the geardriven bit except that the number of responses is preferably inaccordance with the bit rotation which is critical rather than theturbine rotation if it should happen to be of the gear driven type.

I claim:

1. A method for continuously measuring the rotational speed of afluid-driven turbine mounted adjacent the lower end of a drill pipe andwhile located adjacent the bottom of a drill hole which comprises:circulating drilling fluid down the drill pipe to drive said turbine;periodically varying the resistance to flow of said fluid, at a pointadjacent said turbine, at a frequency which bears a simultaneous,predetermined relation to the rotational speed of said turbine and whichfrequency is a multiple fraction greater than one of the rotationalspeed of the turbine thereby generating pressure pulses in the flowingdrilling fluid having a frequency which is a multiple fraction greaterthan one of the rotational speed of the turbine and which pulses aretransmitted through the flowing drilling fluid to a point adjacent thetop of such drill pipe; and intercepting said pusles at said point toobtain thereby a signal bearing a substantially simultaneous,predetermined relationship to the frequency of said pulses.

2. Apparatus for making turbodrill rotational speed measurements whiledrilling comprising: a drill stern having a fluid circulating ducttherethrough; a turbodrill member, including a non-rotating housing anda rotatable turbine, attached to said drill stem; pump means forcirculating fluid down through said duct to said turbine; a cylindricalrotor member coupled to said turbine for rotation therewith andpositioned within said housing; means forming an opening in the curvedsurface of said rotor member; inwardly extending fluid flow restrictionmeans formed on the wall of said housing adjacent said rotor member;transducer means for detecting the variations of resistance to flow offluid through said duct pro duced as the opening in said rotor memberpasses said restriction means upon rotation of said rotor means by saidturbine and for producing electrical signals of a 5 frequency bearing apredetermined relation to the rotational speed of said rotor; and meansfor indicating said signals.

3. Apparatus for making turbodrill speed measurements while drillingcomprising: a drill stem having a fluid circulating duct therethrough; aturbodrill member, includ ing a non-rotating housing and a rotatableturbine, attached to said drill stem; pump means for circulating fluiddown through said duct to said turbine; a cylindrical rotor coupled tosaid turbine for rotation therewith; means forming an opening in thecurved surface of said rotor; a pinion gear eccentrically mounted on thetop of said rotor for the rotation therewith; gear means secured to theinner wall of said housing to mesh with said pinion References Cited inthe file of this patent UNITED STATES PATENTS Hassle-r July 31, 1945Arps Oct. 3, 1950

